Topographic Maps
One way to see isolines at
work…do you know what type of
isoline is used in Topo Maps?
OK…first of all..
• What is a Topographic Map?
• A TOPOGRAPHIC map is a 2 dimensional
model of how a certain landscape looks
• What is a contour line?
• On a topographic map, the isolines
connect point of equal elevation
• You need to try to use your imagination to
see what the landscape might look like in
3-D (in real life)
Top and Side View of Island 1.1
Island 1.1
• Which part of the island has the steepest
slope? (use the profile view to help you)
• That’s right, the EAST side!
• Which side is relatively flat?
• Of course! The West Side!
Island 1.1
• Ok, so now….MARK the highest point on
the island profile with an “H”
• Now MARK the highest point on the top
view with an “H”
Island 1.1
• What do you notice about the spacing of
the contour lines on the steep side of the
island?
• Yup, they’re spaced CLOSE TOGETHER
Island 1.1
• What about the spacing of the contour
lines on the “flat” (level) side of the island?
• Uh huh – they’re spaced FAR APART!
Island 1.1
• If the elevation of sea level is 0 meters, and each
contour line 10 meters higher than the last, LABEL each
contour line on the top view of the island.
• How high is the highest contour line on the map?
• That’s right – 50 meters!
20
10
30
Diagram 1.1
• What is a contour interval?
• A contour interval is the difference in elevation
between 2 consecutive lines on a topo map
• CONTOUR INTERVALS remain the same for
the entire map!!
• So, what is the contour int. of diagram 1.1?
10
20
30
Diagram 1.1
• Notice how the top contour line (the 50th) is
darkened more than the others
• Every 5th contour line (sometimes 4th) is
darkened in for easier reading
• These darkened lines are called “INDEX
CONTOURS” and are in whole round numbers
(like 50, 100, 200, etc.)
Ok, now for a NEATO trick!
• There is a way to calculate a contour
interval!
• This is VERY helpful if you have trouble
figuring it out
• You subtract 2 known contour lines from
each other and then just divide that
number by the number of SPACES
between the 2 lines you just subtracted!
Holy Moly that was a mouthful..
• Check out how easy this is though!
• I will show you 3 maps, and we will figure
out the contour intervals together
• Ready????
• Let’s do it!
Map A
• What is the contour interval here?
• 40-0=40
• 40 divided by 4 spaces = 10 m!!
Map B
• What is the contour interval here?
• 60-0 = 60
• 60 divided by 3 spaces = 20m!
Finally, Map C
• What’s the contour interval here?
• 100-0 = 100
• 100 divided by 4 spaces = 25m
Moving Along…
• To show elevations of land that GOES DOWN INTO
Earth like a mine, quarry, or sinkhole, a SPECIAL
contour line is used
• It’s called a HACHURE line, and looks like what you
have in your notes!
• The small “whiskers” always point towards the lower
elevation
• The 1st hachure line is always given the same value as
the NON-HACHURE contour line before it
• Ok, so let’s try this…..
Diagram 1.2
• OK, label the contour
lines on diagram 1.2
• The C.I. is 10m
• The depression has
been labeled for you
• Remember, the
hachure line has been
given the SAME value
as the last non
hachure line before!
10
20
How did you do?
I know, this stuff is easy, yo!
OK, now for some practice..
• Ok, now it’s time for you to label the next 2
diagrams COMPLETELY
• Label ALL lines
• The contour intervals have been given
beneath the diagrams
• Go to it, and ask for help if you don’t
understand!
How did you do?
What is Relief?
• Pepto Bismol!!!
• Actually, it’s the way the landscape (the shape of
Earth’s surface) is portrayed on a map –
mountains, hills, valleys, plateaus, plains
(lowlands), etc.
• A relief map is a map that shows all of these
things in 3D (with raised surfaces and
everything)
• This is different than a topo map – they show the
landscape in 2D (on flat paper)
Compass Rose
• A compass rose is a set of axes that have
directions labeled on them
• I know many of you have seen simple
ones before….
They look like this!!
Which direction is missing from the list?
OK, so label the one YOU
have..
north (N)
south (S)
east (E)
west (W)
northeast (NE)
northwest
(NW)
southeast (SE) southwest (SW) east-northeast
(ENE)
east-southeast
(ESE)
west-southwest north-northwest north-northeast south-southeast
(WSW)
(NNW)
(NNE)
(SSE)
west-northwest
(WNW) 3
Which direction is missing from the list?? ______________________________________________
How did you do?
Let’s discuss a few things…